Wireless systems typically require a defined set of antenna characteristics, such as frequency, polarization, and gain pattern. However, some applications may require varying antenna characteristics to suit a shifting environment or a set of scenarios that may not have predefined requirements. In such cases, it may be more convenient and cost effective to utilize a reconfigurable antenna than multiple antennas. For example, an application may require an antenna that can be used to receive left-hand circular polarized (LHCP) signals in some situations and right-hand circular polarized (RHCP) signals in other situations and a single configurable antenna may be advantageous over a multi-antenna solution.
Many types of reconfigurable antennas have been developed. Some are based on electrical tuning or switching utilizing varactors, PIN diodes, or RF MEMS switches. These electronic devices are used for shorting or opening sections of the antenna to affect its polarization or its resonant frequency. Other reconfigurable antenna designs have utilized optical devices or substrate materials with tunable characteristics like electric field tunable liquid crystals or magnetic field tunable ferrites. Mechanically reconfigurable antennas have also been designed using actuators or manual reconfiguration. While reconfigurable antennas using electronic devices or mechanical actuation have the advantage of agility, manually reconfigurable antennas can be very low cost and employed without external biasing or power requirements.